Viruses are important pathogens of both humans and animals. Outbreak of a virus infection often results from introduction of a new virus (such as HIV, West Nile Virus, SARS), or from introduction of a new strain of a well known virus to an immunologically naïve population, e.g. influenza.
Despite the importance of the recent outbreaks of West Nile Virus and SARS, influenza is still one of the most prevalent and significant viral infections. Although the availability of formalin-inactivated trivalent vaccines has reduced the impact of influenza epidemics, this virus is still associated with significant morbidity and mortality worldwide. It infects 10-20% of the total population during seasonal epidemics, resulting in between three to five million cases of severe illness and at least 250,000 to 500,000 deaths each year worldwide (World Health Organization, W.H.O., Global Influenza Program, September 2003 and W.H.O. Fact Sheet, March 2003). In the U.S.A. alone, more than 100 million cases are reported each year, causing 20,000 deaths and a consequent strong economic impact, estimated at around 22.9 billion dollars for 1995 (American Lung Association, 2002). W.H.O. has estimated the total burden at around 71-167 billion dollars per year (W.H.O. Fact Sheet, March 2003).
Until recently, amantadine and rimantadine were used for the treatment of influenza infection, but these are now believed to be associated with severe adverse effects (including delirium and seizures which occur mostly in elderly persons on higher doses). When used for prophylaxis of pandemic influenza at lower doses, such adverse events are less apparent. In addition, the virus tends to develop resistance to these drugs (Steinhaur et al., 1991).
A new class of antivirals, the neuraminidase inhibitors, has recently been developed. Such drugs as zanamivir and oseltamivir, which have fewer adverse side effects (although zanamivir may exacerbate asthma or other chronic lung diseases) are nevertheless expensive and currently not available for use in many countries (W.H.O. Fact Sheet, March 2003). Influenza may develop resistance to neuroaminidase inhibitors too (McKimm-Berschkin, 2000; Gubavera, et al. 2002).
Many herbs and spices, among them also cinnamon, have been shown to feature antimicrobial and chemoprotective activities, (Lay and Roy, 2004). Extracts from cinnamon obtained by organic solvents (for example as in Velluti et al, 2004), typically contain the following ingredients: Eugenol (82%), Caryophylene (4.6%), Eugenyl acetate (2.1%), Linalool (1.8%), Cinnamaldehyde (1%), Cinnamyl alcohol acetate (1%), 2-Propyl benzodioxol (1%), and Cubebene (<1%). These extracts, which are in fact essential oils, have shown to exhibit antifungal activity. (Velluti et al., 2003 and Velluti et al, 2004).
Other cinnamon bark essentials oils had antibacterial activity against Bacillus cereus, (Valero and Salmeron, 2003); as well as antibacterial and antifungal activities, (Kalemba and Kunicka, 2003 and Mau et al., 2001).
Cinnamon hydrophobic fractions extracted in organic solvents had antibacterial activity against Helicobacter pylori, (Tabak, M. et al., 1999); antifungal activity for fungi causing respiratory tract mycoses, (Singh, H. B. et al., 1995), and anti HIV-1 activity caused by inhibiting the reverse transcription, (Yamasaki et al., 1998).
Compounds obtained from cinnamon are also used for other indications such as the use of cinnamon powder for reducing serum glucose triglycerides, LDL cholesterol and total cholesterol, (Khan et al, 2003); water extracts of cinnamon were used as antioxidants (Murcia et al, 2004); were shown to prevent insulin resistance, (Qin et al., 2004); and were also shown to inhibit Na+/K+ ATPase and Cu2+ ATPase, (Usta et al., 2003). Essential oil extract obtained from cinnamon were further shown to improve digestion (Hernandez et al., 2004).